(1) Field of the Invention
The present invention related to a circuit for processing a digital signal such as a digital video signal having a blanking interval. The present invention relates specifically to a digital processing circuit in which signal processings in a plurality of signal processing blocks are controlled on the basis of operation control data added into the blanking interval of the input digital signal, whereby the circuit construction can be simplified and the complex signal processing can be carried out.
(2) Background of the Art
Photographing equipment such as a video camera generally converts an optical image on a surface of a photographic (image pick-up) element into an electrical video signal and produces a standard NTSC (National Television System Committee) color television signal under various signal processings for the video signal such as a white balance adjustment and gamma correction, etc.
In addition, in such a photographic equipment, the NTSC standard color television signal is provided with a blanking interval, i.e., a line returning interval of scanning lines during which no video image is reproduced. The blanking intervals are time intervals between the video signal effective intervals, i.e., between the effective signal segments containing video information.
Recently, along with developments of digital signal processing techniques, a digital signal processing circuit has been used in a signal processing system for video signals.
For example, as shown in FIG. 1, such a digital signal processing circuit includes a data input terminal 101 to which an input digital signal is supplied, a plurality of signal processing blocks 102, 103, and 104 for carrying out predetermined signal processings such as a white balance adjustment and gamma correction for the input digital signal D.sub.in, and a data output terminal 105, each circuit block and terminal being connected in series with each other.
Furthermore, a control circuit block 106 for controlling the signal processing of each of the signal processing blocks 102, 103, and 104 is connected to each signal processing block 102, 103, and 104 via respective control signal lines 107, 108, and 109.
In the above-described signal processing circuit, each signal processing block 102, 103, and 104 is formed of an IC (Integrated Circuit). Their operation controls are directly carried out by means of the above-described control block 106 via each control signal line 107, 108, and 109 so that the predetermined signal processings for the input digital signal D.sub.in are carried out at the respective signal processing blocks 102, 103, and 104 to output the output digital processed signal D.sub.out via the data output terminal 105.
The number of signal lines connected to the respective signal processing blocks 102, 103, 104 formed as above-described from ICs, in the video signal processing circuit, amount to approximately more than 100, including the signal lines for outputting and inputting data of color components such as red (R), green (G), and blue(B) of the image pick-up signals, the control signal lines 107, 108 and 109, power supply lines and clock signal lines.
A digital signal processing circuit formed from integrations of several large-scale ICs also has the problems of an excessive number of signal lines and of very complex circuit construction.
Therefore, a digital signal processing circuit is demanded which can carry out the more complex signal processings for the input digital signal. The signal processing blocks for such circuit must be capable of inputting and outputting large amounts of data including that for operation controls. One of methods for inputting and outputting tremendous amounts of data without increase in the number of signal lines connected to the signal processing blocks includes, e.g., the data serial transmission method. However, time errors are generated for the signal processings of the video signals, and, accordingly, a hardware for the reception and transmission of data is needed.
Consequently, there has been no sufficient method of solving these problems up to this time.